The first recorded mention of a leprechaun goes back to the 8th century, coming from the word luchorpán, meaning "little body" to describe water spirits, according to John and Caitlin Matthews in The Element Encyclopedia of Magical Creatures.

Another possible origin is the Irish god Lugh, whose Welch variant is known as one of the "Three Golden Shoemakers."

There's also the Irish fairy Cluricaune, "a cunning spirit who haunts cellars, drinks, smokes and plays tricks," the Matthewses write. Cluricaune was popularized in a 1825 publication called Fairy Legends.

Corned beef and cabbage

Although a classic St. Patrick's Day meal, corned beef and cabbage is more American than Irish.

Irish Americans in the 19th century were mostly poor. The most affordable meat available was corned beef, according to Cronin.

And cabbage? "It's a spring vegetable and it's cheap," Cronin said.

Guinness

The Irish stout is the drink of choice on St. Patrick's Day.

On a typical day, Americans drink about 600,000 pints of the Dublin-based beer. But on St. Patrick's Day, about 3 million pints of Guinness are downed, according to Guinness in an email to USA TODAY Network.

Planning on drinking a pint on Monday? Tips from Guinness on the perfect pour: Tilt the glass at 45 degrees when pouring until it is three-quarters full, then let the beer settle before filling the glass completely to the top.